The twins have been crucial to the new research, as they are genetically identical but one has developed cancer whereas the other has not. The scientists found that the girls’ blood contains genetically abnormal cells known as pre-leukaemic cells. These were formed by a mutation known as translocation, in which two genes fuse to create an abnormal new one. This random event happened in a single cell in one of the twins while they were still in the womb. As the twins shared a placenta, the original mutant’s daughter cells populated the blood of both sisters.
The discovery will help doctors to monitor Isabella, and children like her, so that further genetic damage in her pre-leukaemic stem cells is caught early. By the time she is 14, her pre-leukaemic stem cells should have died naturally.
“Pre-leukaemic cells are still evident, so the sword of Damocles is still hanging there,” Dr Ancliff said. “Hopefully, we will see them disappear.” (Times)

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